1. Field of the Invention
The present invention relates generally to etching devices and, more particularly, to a metal die acid etch apparatus having a bath of acid etch solution that is allowed to continuously overflow from a predetermined level at the top of the bath and to be at least partially recirculated.
2. Discussion of the Prior Art
A conventional metal die acid etch apparatus comprises an open-topped tank for holding an acid etch solution, and a hood assembly on which a metal die is supported over the tank. A plurality of paddle wheels or sprayers are provided in the tank for projecting the solution onto the metal die so that the solution etches the die as desired.
It is a known requirement in such conventional constructions that the temperature of the solution be maintained within about .+-.1.degree. F. Accordingly, it is known to provide a heater and/or cooler which adjusts and maintains the temperature of the solution in the tank during an etching operation. It is also necessary, especially where paddle wheels are employed to splash solution onto the metal die, to closely control the volume of solution within the tank in order to provide a consistent exposure of the die to the solution.
One problem arising from the use of the conventional construction is that the tank typically requires a relatively large volume of solution, and it is always necessary to maintain this volume, even if the apparatus is to be used to etch only a single metal die. It is not possible to operate the apparatus with less than this required volume, and the entire volume of solution must be heated or cooled to the necessary temperature, and thereafter maintained at this temperature.
Another problem encountered with the conventional construction is that metal particles from the die fall from the die into the tank during an etching process and are re-projected onto the metal die by the paddle wheels or sprayers. These metal particles interfere with the desired chemical process between the solution and the metal die, and adversely effect the quality of the etching.